erichkeane added inline comments.
================
Comment at: clang/lib/AST/ExprConstant.cpp:4989
if (SS->getCond()->isValueDependent()) {
if (!EvaluateDependentExpr(SS->getCond(), Info))
return ESR_Failed;
----------------
shafik wrote:
> As far as I can tell `Value` will still not be set if we don't return here
> and we will still crash when we attempt to compare `Value` below:
>
> ```
> LHS <= Value && Value <= RHS
> ```
I don't understand the comment? We're returning 'failed', aren't we? Except
now `EvaluateDependentExpr`is where the failure is coming from?
================
Comment at: clang/lib/AST/ExprConstant.cpp:4893
+ // Stop evaluate if E is a RecoveryExpr.
+ if (isa<RecoveryExpr>(E))
+ return false;
----------------
yronglin wrote:
> yronglin wrote:
> > erichkeane wrote:
> > > I'd probably suggest `E->containsErrors()` instead, to cover cases where
> > > we're not the 'root' of a recovery expr? So something like:
> > >
> > > `switch(func_call(unknown_value))`
> > >
> > > should create a dependent call expr, but would still contain errors.
> > Thanks! Use `E->containsErrors()` and added into release note.
> Seems check error inside `EvaluateDependentExpr` will missing diagnostic
> messages.
>
> This case was introduced in D84637
> ```
> constexpr int test5() { // expected-error {{constexpr function never produce}}
> for (;; a++); // expected-error {{use of undeclared identifier}} \
> expected-note {{constexpr evaluation hit maximum step
> limit; possible infinite loop?}}
> return 1;
> }
> ```
> ```
> ./main.cpp:2:11: error: use of undeclared identifier 'a'
> 2 | for (;; a++); // expected-error {{use of undeclared identifier}} \
> | ^
> 1 error generated.
> ```
> But I think the `infinite loop` diagnostic is unnecessary, should we update
> the test case? WDYT?
Huh... thats interesting. The 'Info.noteSideEffect' is sufficient to do that?
Looking closer, I wonder if this is the wrong fix and his original idea was
better. It seems that this already has a 'containsError' check at the end, and
should if it doesn't have side effects.
I was hoping to have the problem generalized, but I think I was wrong, and we
should go back to just fixing the 'switch' statements.
================
Comment at: clang/lib/AST/ExprConstant.cpp:4988
+ if (SS->getCond()->containsErrors() ||
+ !EvaluateDependentExpr(SS->getCond(), Info))
return ESR_Failed;
----------------
shafik wrote:
> yronglin wrote:
> > erichkeane wrote:
> > > It seems to me that the 'better' solution is to make
> > > EvaluateDependentExpr (or one of its children) be RecoveryExpr aware, and
> > > result in a failed value instead. That way we get this 'fix' for more
> > > than just switch statements.
> > Thanks for your review!
> Erich so there are places in `ExprConstant.cpp` where if we
> `isValueDependent()` we bail out like in the `Stmt::ReturnStmtClass` case
> inside `EvaluateStmt1()`. The gist I get from the comment there is
>
> ```cpp
> // We know we returned, but we don't know what the value is.
> ```
>
> Is that not correct or does it depend on each specific case?
TBH, i don't have a good idea of that. I spent a little time digging here, but
the constant evaluator isn't my forte.
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D153296/new/
https://reviews.llvm.org/D153296
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